The present invention relates to a developing material supplying device for supplying developing material to an electrostatic latent image developing apparatus for use in an electrophotographic copying apparatus and the like.
Commonly, in the electrostatic latent image developing apparatus as described above, it is necessary to supply the developing material for replenishment at proper intervals as the development proceeds, and the amount of the developing material to be supplied for the replenishment must be properly measured so as not to be excessively large or excessively small.
In order to meet the requirements as stated above, there have conventionally been proposed and put into practical use various developing material supplying devices, the representative one of which includes an arrangement wherein a developing material supplying roller having V-shaped notches or recessed portions in part of its peripheral surface for the replenishment of the developing material is rotatably provided for being driven at a developing material supplying opening or port formed at the lower part of a developing material storage tank.
Even the known developing material supplying device as described above still has various disadvantages to be overcome, and improvements thereof have been greatly desired.
In view of such a need, the present inventors have carried out a series of experiments and analyses on the above developing material supplying device for clarification of causes of the disadvantages, as a result of which it has been found that:
(i) during the replenishment of the developing material, since the developing material to be replenished tends to be undesirably packed too tightly in the V-shaped recessed portions owing to variations of ambient conditions such as ambient humidity, etc., the amount of the developing material to be measured by the V-shaped recesses for the replenishment to the developing apparatus is liable to vary to a large extent.
(ii) moreover, since the seal provided at the developing material supplying opening in the lower part of the developing material storage tank for preventing the developing material from leaking is not perfect, the amount of the developing material to be supplied to the developing apparatus tends to vary due to undesirable leakage of the developing material. Mere improvements in the degree of closeness of contact between the wall surface (the wall surface defining the developing material supplying opening) of the storage tank and the peripheral surface of the developing material supplying roller result in an abnormal increase of rotational driving torque for said supplying roller, with consequent troubles arising therefrom, and thus, it has been necessary to tolerate the imperfectness of the seal as described above.
(iii) Furthermore, due to the fact that the amount of rotation of the developing material supplying roller is determined by the time period during which said supplying roller is coupled with a driving source, errors tend to take place in the amount of rotation, thus making it impossible to achieve a stable control of the amount of rotation of the supplying roller in a strict sense, and following the errors in the amount of rotation as described above, the amount of the developing material to be supplied to the developing device also varies to a certain extent. During the experiments and analyses as described above, it has simultaneously been confirmed by the present inventors that in the conventional developing material supplying device as described above, the developing material is undesirably compressed and tends to solidify in a position between the developing material supplying opening and developing material supplying roller following rotation of said supplying roller.